A team led by Uppsala University and Linnaeus University researchers has identified a trio of peptides in plasma that could prove useful biomarkers for autism.
In a study published last week in Translational Psychiatry, the scientists used a combination of mass spec techniques to profile the plasma of 28 children with autism spectrum disorders, identifying three differentially expressed peptides corresponding to fragments of the C3 complement protein.
Jonas Bergquist, an Uppsala University researcher and author on the paper, told ProteoMonitor that the findings were "still preliminary," but, he added, C3 complement protein "has been connected to other neuropsychiatric disorders" in past studies, "so we think these findings are pretty interesting."
The study examined blood samples from 28 children with ASD and 30 controls recruited from the autism rehabilitation center at the University of Social Welfare and Rehabilitation Sciences in Tehran, Iran.
The initial discovery work was done at Sweden's Linnaeus University on a SELDI-TOF mass spec instrument. As Bergquist noted, however, SELDI-TOF has been widely dismissed as a platform for protein biomarker work due to challenges such as issues with reproducibility. Given these concerns, the researchers followed up the SELDI-TOF analysis with MALDI-TOF/TOF analysis on a Bruker Ultraflex II instrument and then confirmed this MALDI-based work with analysis via FT-ICR mass spec.
Bergquist said that he was "not in favor of SELDI mass spectrometry at all." However, he noted, the approach "can be useful if you know what you're doing and you're very careful with the sample preparation."
In particular, Bergquist said, due to its high speed "SELDI can be a nice screening device if you know how to handle your sample." However, he added, "for identifying and verifying [analytes] it's pretty useless."
By following up the initial SELDI screening with higher resolution MALDI-TOF/TOF-MS, the researchers were able to "validate their [initial] findings, identify the [peptides], and also measure the quantitative differences" in expression, Bergquist said.
Moving forward, the researchers now hope to validate their results in larger cohorts using samples collected from other clinics, he said, adding that they are "now in contact with colleagues around Sweden who are willing to help us find some patients to follow up on."
The researchers would also like to validate their findings against patients with other neuropsychiatric disorders to determine how specific the C3 complement peptides are to ASD, as well as test the markers in a longitudinal study to see what prognostic value they might have, Bergquist said.
He noted that, "although it hurts me as a mass spectrometrist," the need for high throughput in clinical validation studies would likely lead the researchers to move work on the markers from mass spec to an immunoassay platform. He said that the team was currently looking into measuring the markers via proximity ligation assay technology, which was developed in the lab of Uppsala researcher Ulf Landegren and has since been commercialized by the Swedish biotech firm Olink Biosciences.
Although proteomics-based ASD research has not been as widespread as genomic efforts, Bergquist and his colleagues are not alone in looking for protein markers for the disorder. As they noted in their paper, past proteomic studies have linked a single-nucleotide polymorphism in glyoxalase I to ASD as well as differential expression of apolipoproteins and other components of complement proteins.
And at the US Human Proteome Organization annual meeting this month in San Francisco, researchers from Boston-based biotech firm Berg Pharma presented results from an ASD biomarker study the company had conducted.
Combining genomic, proteomic, and metabolomic analyses of 20 ASD patients and 20 controls, the Berg researchers identified three proteins – SPTAN1, CORO1A, and GLUD1 as potential ASD biomarkers.
According to the study results, these three markers are potentially key "hubs" for the disease, Niven Narain, Berg president and chief technology officer, told ProteoMonitor, but, in fact, the company identified roughly 150 potential markers in their research.
The company is now working with Boston-area hospitals and foundations to collect samples for a larger validation study, Narain said.
Ultimately, Berg chief operating officer Shen Luan told ProteoMonitor, the firm hopes to develop a commercial diagnostic for ASD, which it would run out of its CLIA certified laboratory.
"The field needs diagnostics for these kids," he said, noting that current diagnostic techniques, which typically rely on the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, use "pretty loose criteria to put a kid on a spectrum."
"The field needs a biomarker for ASD in general, so that's our goal – to take it to [commercialization] after clinical validation," Luan said.
Bergquist likewise noted the lack of objective measures in the field. "Today we look at the symptoms and we draw conclusions that are symptom-based … [but] there aren't any strong markers really to use," he said. "That's why there is big interest in the field to find something more objective."
Such markers "could help in the diagnosis and also maybe could make clinicians and parents more aware of what is going on at an earlier stage," Bergquist said.
"The other point is that if these markers turn out to give us more information on the biological background behind these neuropsychiatric disorders, that of course could aid in [developing] potential treatments."
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